1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
24 */
25
26 /*
27 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
28 * Use is subject to license terms.
29 */
30
31 #pragma weak nexttoward = __nexttoward
32
33 /*
34 * nexttoward(x, y) delivers the next representable number after x
35 * in the direction of y. If x and y are both zero, the result is
36 * zero with the same sign as y. If either x or y is NaN, the result
37 * is NaN.
38 *
39 * If x != y and the result is infinite, overflow is raised; if
40 * x != y and the result is subnormal or zero, underflow is raised.
41 * (This is wrong, but it's what C99 apparently wants.)
42 */
43
44 #include "libm.h"
45
46 #if defined(__sparc)
47 static union {
48 unsigned i[2];
49 double d;
50 } C[] = {
51 0x00100000, 0, 0x7fe00000, 0, 0x7fffffff, 0xffffffff
52 };
53
54 #define tiny C[0].d
55 #define huge C[1].d
56 #define qnan C[2].d
57
58 enum fcc_type {
59 fcc_equal = 0, fcc_less = 1, fcc_greater = 2, fcc_unordered = 3
60 };
61
62 #ifdef __sparcv9
63 #define _Q_cmp _Qp_cmp
64 #endif
65
66 extern enum fcc_type _Q_cmp(const long double *, const long double *);
67
68 double
69 __nexttoward(double x, long double y)
70 {
71 union {
72 unsigned i[2];
73 double d;
74 } xx;
75 union {
76 unsigned i[4];
77 long double q;
78 } yy;
79
80 long double lx;
81 unsigned hx;
82 volatile double dummy;
83 enum fcc_type rel;
84
85 /*
86 * It would be somewhat more efficient to check for NaN and
87 * zero operands before converting x to long double and then
88 * to code the comparison in line rather than calling _Q_cmp.
89 * However, since this code probably won't get used much,
90 * I'm opting in favor of simplicity instead.
91 */
92 lx = xx.d = x;
93 hx = (xx.i[0] & ~0x80000000) | xx.i[1];
94
95 /* check for each of four possible orderings */
96 rel = _Q_cmp(&lx, &y);
97
98 if (rel == fcc_unordered)
99 return (qnan);
100
101 if (rel == fcc_equal) {
102 if (hx == 0) { /* x is zero; return zero with y's sign */
103 yy.q = y;
104 xx.i[0] = yy.i[0];
105 return (xx.d);
106 }
107
108 return (x);
109 }
110
111 if (rel == fcc_less) {
112 if (hx == 0) { /* x is zero */
113 xx.i[0] = 0;
114 xx.i[1] = 0x00000001;
115 } else if ((int)xx.i[0] >= 0) { /* x is positive */
116 if (++xx.i[1] == 0)
117 xx.i[0]++;
118 } else {
119 if (xx.i[1]-- == 0)
120 xx.i[0]--;
121 }
122 } else {
123 if (hx == 0) { /* x is zero */
124 xx.i[0] = 0x80000000;
125 xx.i[1] = 0x00000001;
126 } else if ((int)xx.i[0] >= 0) { /* x is positive */
127 if (xx.i[1]-- == 0)
128 xx.i[0]--;
129 } else {
130 if (++xx.i[1] == 0)
131 xx.i[0]++;
132 }
133 }
134
135 /* raise exceptions as needed */
136 hx = xx.i[0] & ~0x80000000;
137
138 if (hx == 0x7ff00000) {
139 dummy = huge;
140 dummy *= huge;
141 } else if (hx < 0x00100000) {
142 dummy = tiny;
143 dummy *= tiny;
144 }
145
146 return (xx.d);
147 }
148 #elif defined(__x86)
149 static union {
150 unsigned i[2];
151 double d;
152 } C[] = {
153 0, 0x00100000, 0, 0x7fe00000, };
154
155 #define tiny C[0].d
156 #define huge C[1].d
157
158 double
159 __nexttoward(double x, long double y)
160 {
161 union {
162 unsigned i[2];
163 double d;
164 } xx;
165
166 unsigned hx;
167 long double lx;
168 volatile double dummy;
169
170 lx = xx.d = x;
171 hx = (xx.i[1] & ~0x80000000) | xx.i[0];
172
173 /* check for each of four possible orderings */
174 if (isunordered(lx, y))
175 return ((double)(lx + y));
176
177 if (lx == y)
178 return ((double)y);
179
180 if (lx < y) {
181 if (hx == 0) { /* x is zero */
182 xx.i[0] = 0x00000001;
183 xx.i[1] = 0;
184 } else if ((int)xx.i[1] >= 0) { /* x is positive */
185 if (++xx.i[0] == 0)
186 xx.i[1]++;
187 } else {
188 if (xx.i[0]-- == 0)
189 xx.i[1]--;
190 }
191 } else {
192 if (hx == 0) { /* x is zero */
193 xx.i[0] = 0x00000001;
194 xx.i[1] = 0x80000000;
195 } else if ((int)xx.i[1] >= 0) { /* x is positive */
196 if (xx.i[0]-- == 0)
197 xx.i[1]--;
198 } else {
199 if (++xx.i[0] == 0)
200 xx.i[1]++;
201 }
202 }
203
204 /* raise exceptions as needed */
205 hx = xx.i[1] & ~0x80000000;
206
207 if (hx == 0x7ff00000) {
208 dummy = huge;
209 dummy *= huge;
210 } else if (hx < 0x00100000) {
211 dummy = tiny;
212 dummy *= tiny;
213 }
214
215 return (xx.d);
216 }
217 #else
218 #error Unknown architecture
219 #endif